Particles are produced during the combustion of fuel in an internal combustion engine. Since these particles are damaging to the health, legislators have defined limiting values for these emissions. In order to be able to comply with these particle limiting values, particle filters are used, in particular, in the exhaust train of modern diesel engines in motor vehicles.
These particle filters are typically embodied as wall-flow filters based on ceramic materials. Legislators have also required that the functionality of the filter is monitored, specifically with the aid of what is referred to as “on-board diagnosis”. In order to satisfy these requirements for monitoring, a sensor monitors the filter functionality of the wall-flow filter. This particle sensor is arranged downstream of the particle filter and measures the concentration of particles in the exhaust gas. If the particle filter is intact, a low particle concentration is measured. If the filter is damaged, an abnormally high concentration is determined.
In such a method for checking the functionality of a particle filter, correct measurement by the particle sensor is critical, since otherwise incorrect results lead to an incorrect particle filter diagnosis. The problems center on reliably detecting whether the sensor is measuring correctly.